The present invention relates to a plate type heat exchanger, and more particularly, to a heat exchanger for refrigerating and air conditioning, suitable for a vapor compression type refrigeration cycle.
Conventionally, in order to make a plate type heat exchanger compact and improve its heat transfer performance, it has been known to form heat-transfer surface elements having mountains and valleys in a thicknesswise direction of a plate and to provide micro fins on surfaces of the elements, which arrangement is described in International Publication WO00/16029.
The above-described conventional art is designed with use for the vapor compression type refrigeration cycle in mind, and therefore, it has been difficult to adequately ensure pressure tightness in use of high-pressure refrigerants typified by R410A and carbon dioxide. Also, when it is used as an evaporator such as a chiller unit, there is a fear that cold water freezes and seals break to cause mixing of water and a refrigerant when a working temperature on a refrigeration cycle side greatly decreases.